president obama called the bombings a cowardly act. >> if you want to know who we are, who mark is, how we respond to evil, that's it. selflessly, compassionately, unafraid. >> reporter: surveillance cameras like this one nearby the crime scene are proving crucial to investigators. they are using them, combined with any photos they can find nhopes of-- in hopes of catching the suspect. >> reporter: runners took to the scene to pick up their belongings and medals. leah says, despite the attack, she's going to keep competing. >> people aren't going to stop running. in fact, they'll probably be running even more. >> reporter: the area will be closed off, at least until thursday. >> reporter: despite the countless tips they have received, authorities are still telling us, they have no clear suspect. earlier, they had been talking to a saudi man. they each executed a search warrant on his home. we're now being told he -- instead of being a suspect, rather, he was a victim himself. he was a spectator who was hurt when those bombs were detonated. reporting live in boston, vinita nair, back to